[Catalyst] C::P::PageCache patch for reducing duplicate processing

[Toby Corkindale]

Perrin Harkins wrote:
> Toby Corkindale wrote:
>> One of the aims of my patch is to avoid the expense of having numerous 
>> processes produce the same code simultaneously. So on the initial bunch 
>> of requests, I'll still try and have the code delay all-but-one of them 
>> from building the page.
> 
> Presumably this only happens when a new cached page suddenly becomes 
> available and is instantly in high demand.  It's not very frequent.  In 
> my opinion, that isn't worth the danger of messing with something as 
> potentially troublesome as locks that block page generation, but I 
> suppose no one is forced to use the locking.

Good point.
I'll try and implement the features so they can be enabled separately.